Project 4. Project Summary. Project 4 is a continuation of our basic-research intracranial recordings in humans, which were scattered across Aims in multiple Projects in the current funding period and have now been collected in one focused Project. It is co-directed by Richard Andersen and Ueli Rutishauser, both of whom are also on our current Conte Center. Its overarching Aim is to use single-unit recordings in humans to understand the representations and circuits for social inference and its contextual modulation, with an emphasis on comparing this to representations of one's own states. It links to other Projects: Aim 1 will investigate the responses of amygdala neurons to social threat, a question linked to Project 3. Aim 2 will investigate the responses of posterior parietal neurons in representing another person's actions from which we could learn, a question linked to Project 1. These links are reflected in the personnel of Project 4, which includes PIs from other Projects (Adolphs, O'Doherty, Mobbs) as well as shared post-docs and students. The Aims of Project 4 map onto recordings in two distinct patient populations. Aims 1 and 3 will be led by Rutishauser, and tested with single-unit recordings from the amygdala and prefrontal cortex in epilepsy patients (10 per year), through a subcontract to Cedars-Sinai Medical Center. Aims 2 and 4 will be led primarily by Richard Andersen, and tested with single-unit recordings from the posterior parietal cortex in rare patients who have brain-machine interfaces implanted chronically for control of neural prosthetics (tested at a rehabilitation center close to Caltech). Aim 1 will record the responses of neurons in the prefrontal cortex and amygdala to social stimuli such as faces and a range of threats. It will investigate the category-selectivity of neurons, and ask how this is modulated by attention, using concurrent eyetracking. Aim 2 will record primarily in the posterior parietal cortex, but also include some experiments with recordings in amygdala and prefrontal cortex, and examine how the observation and execution of actions are represented by these neurons (a question related to so-called ?mirror neurons?). It also includes a close link to Project 1 in testing whether single neurons encode signals for observational learning. Aim 3 will investigate error signals in a Stroop task by recording from neurons in the anterior cingulate cortex and supplementary motor cortex in epilepsy patients; it will also feature an observational Stroop task, where the subject sees the errors made by another person. This Aim will also be conducted, in the same patients, using fMRI (prior to their electrode implantations). Aim 4 will capitalize on the ability record in posterior parietal cortex in the brain-machine interface patients from over a year, and will compare recordings done over this long period as a function of state variables such as mood.